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virtio_blk: simplify refcounting
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Implement the ->free_disk method to free the virtio_blk structure only
once the last gendisk reference goes away instead of keeping a local
refcount.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20220215094514.3828912-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Christoph Hellwig authored and Jens Axboe committed Feb 17, 2022
1 parent 185ed42 commit 24b45e6
Showing 1 changed file with 14 additions and 52 deletions.
66 changes: 14 additions & 52 deletions drivers/block/virtio_blk.c
Original file line number Diff line number Diff line change
Expand Up @@ -69,13 +69,6 @@ struct virtio_blk {
/* Process context for config space updates */
struct work_struct config_work;

/*
* Tracks references from block_device_operations open/release and
* virtio_driver probe/remove so this object can be freed once no
* longer in use.
*/
refcount_t refs;

/* What host tells us, plus 2 for header & tailer. */
unsigned int sg_elems;

Expand Down Expand Up @@ -391,43 +384,6 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str)
return err;
}

static void virtblk_get(struct virtio_blk *vblk)
{
refcount_inc(&vblk->refs);
}

static void virtblk_put(struct virtio_blk *vblk)
{
if (refcount_dec_and_test(&vblk->refs)) {
ida_simple_remove(&vd_index_ida, vblk->index);
mutex_destroy(&vblk->vdev_mutex);
kfree(vblk);
}
}

static int virtblk_open(struct block_device *bd, fmode_t mode)
{
struct virtio_blk *vblk = bd->bd_disk->private_data;
int ret = 0;

mutex_lock(&vblk->vdev_mutex);

if (vblk->vdev)
virtblk_get(vblk);
else
ret = -ENXIO;

mutex_unlock(&vblk->vdev_mutex);
return ret;
}

static void virtblk_release(struct gendisk *disk, fmode_t mode)
{
struct virtio_blk *vblk = disk->private_data;

virtblk_put(vblk);
}

/* We provide getgeo only to please some old bootloader/partitioning tools */
static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
{
Expand Down Expand Up @@ -460,11 +416,19 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
return ret;
}

static void virtblk_free_disk(struct gendisk *disk)
{
struct virtio_blk *vblk = disk->private_data;

ida_simple_remove(&vd_index_ida, vblk->index);
mutex_destroy(&vblk->vdev_mutex);
kfree(vblk);
}

static const struct block_device_operations virtblk_fops = {
.owner = THIS_MODULE,
.open = virtblk_open,
.release = virtblk_release,
.getgeo = virtblk_getgeo,
.owner = THIS_MODULE,
.getgeo = virtblk_getgeo,
.free_disk = virtblk_free_disk,
};

static int index_to_minor(int index)
Expand Down Expand Up @@ -791,8 +755,6 @@ static int virtblk_probe(struct virtio_device *vdev)
goto out_free_index;
}

/* This reference is dropped in virtblk_remove(). */
refcount_set(&vblk->refs, 1);
mutex_init(&vblk->vdev_mutex);

vblk->vdev = vdev;
Expand Down Expand Up @@ -970,7 +932,7 @@ static void virtblk_remove(struct virtio_device *vdev)
flush_work(&vblk->config_work);

del_gendisk(vblk->disk);
blk_cleanup_disk(vblk->disk);
blk_cleanup_queue(vblk->disk->queue);
blk_mq_free_tag_set(&vblk->tag_set);

mutex_lock(&vblk->vdev_mutex);
Expand All @@ -986,7 +948,7 @@ static void virtblk_remove(struct virtio_device *vdev)

mutex_unlock(&vblk->vdev_mutex);

virtblk_put(vblk);
put_disk(vblk->disk);
}

#ifdef CONFIG_PM_SLEEP
Expand Down

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